Positive displacement pump

ABSTRACT

A positive displacement pump comprising a pump body having a pump bore, a rotor mounted for rotation in said bore and cooperating with that bore to define at least one pumping cavity, a plurality of slippers or pumping elements in the form of flat leaf springs carried by the periphery of the rotor, each slipper having its intermediate portion sealingly engaged with the surrounding bore wall, one end of each leaf spring being anchored on the rotor and the other being adapted for sliding movement on the rotor to compensate for changes in the working height of the spring as the spring is carried through a pumping arc.

Unite Lewieki iii States Patent 1 Feb.11,1972

[54] POSITIVE DISPLACEMENT PUMP I21] App]. No.: 67,444

[SZl Uh. (ll ..4l8/l56, 418/267 [51 i Int. Cl ..F0lc 5/00, F03c 5/00, F040 1/00 (58] Field of Search AIS/153, 156, 266, 267, 268,

l 56] References Cited UNITED STATES PATENTS 1,989,900 2/1935 Vickers ..418/238 2,485,240 10/1949 Jackson 413/266 Primary Examiner-Carlton R. Croyle Assistant Examiner-Richard E. Gluck Arrorney-John R. Faulkner and Donald 1 Harrington [57] ABSTRACT A positive displacement pump comprising a pump body having a pump bore, a rotor mounted for rotation in said bore and cooperating with that bore to define at least one pumping cavity, a plurality of slippers or pumping elements in the form of flat leaf springs carried by the periphery of the rotor, each slipper having its intermediate portion seailingly engaged with the surrounding bore wall, one end of each leaf spring being anchored on the rotor and the other being adapted for sliding movement on the rotor to compensate for changes in the working height of the spring as the spring is carried through a pumping are.

d Claims, 2 Drawing Figures PATENTED FEB 1 I972 SHEET 1 OF 2 PATENIEDFEB 11972 516391091 SHEET 2 0% 2 I mmm fim/Amm 5mm POSITIVE DISPLACEMENT PUMP GENERAL DESCRIPTION OF THE INVENTION My invention relates generally to positive displacement pumps for pumping fluids. It may be used in an automatic power transmission mechanism for developing circuit pressure in a valve system to control selectively operable clutches and brakes.

Several positive displacement pumps of known design also are capable of being used in this environment, including wellknown vane pumps and slipper pumps. A vane pump would include a pump body having a pumping chamber formed therein within which a pump rotor is mounted rotatably. Vanes carried by the rotor in precision slots carry the vanes in pumping disposition with the outermost ends of the vanes slidably engaging the wall of the pump bore. One such vane pump is shown in US. Pat. No. 2,411,602 and another is shown in US. Pat. No. 1,989,900.

It is known practice also to provide slipper elements in a pump rotor wherein the slippers act as pumping elements as they move radially inwardly and outwardly upon rotation of the rotor through the pumping arc. These slippers also may oscillate about a secondary, transverse axis. The slippers in designs such as this are situated in rotor slots, and their forward or leading edges are adapted to admit high-pressure fluid to the underside of the vanes so that the vanes may sealingly engage the wall of the bore of the pump. Slipper pumps having these features are shown, for example, in US. Pat. Nos. 3,009,420 and 3,009,421.

My improved pump mechanism may be characterized as a positive displacement slipper pump, but the slipper elements are in the form of flat leaf springs rather than in the form of vanes or slippers such as those shown in U.S. Pat. Nos. 3,009,420 and 3,009,421. The leaf springs are carried by the periphery of the rotor and are held in angular shifting disposition relative to the rotor by abutments which are engaged by the trailing edges of the individual flat springs. The intermediate portion of each spring engages the surrounding wall of the pump bore and exerts on the bore a sealing force due to the spring preload. The opposite end of each spring rests on a flat surface formed on the periphery of the rotor and is adapted to shift thereon as the spring deflects during rotation of the rotor.

The springs provide an effective seal between the inlet port and the outlet port. The porting is arranged so that communication is established between the outlet port and the underside of the individual springs during movement of the springs through the pumping arc. Similarly, the inlet port is arranged so that communication is established between the undersides of the individual springs and the inlet side of the pump as the springs traverse the intake are.

There is no need for precision tolerances in the elements of the pump assembly. The cost of manufacture of my improved pump mechanism compared to the cost of manufacture of pump mechanisms of known constructions is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a cross sectional view of my improved pump mechanism as seen from the plane of section line 1-1 of FIG. 2.

FIG. 2 is a cross-sectional view taken along the plane of section line 22 of FIG. 1.

PARTICULAR DESCRIPTION OF THE INVENTION Numeral l designates generally a pump body that is provided with a circular-pumping chamber 12 having a geometric center at 13. l have shown the pumping chamber 12 in the form of a circular bore, although it is not essential that the pumping chamber be circular. Typical pumping chambers of other shapes are illustrated in the above-identified reference patents. If two pumping chambers are provided, the pressure forces may be balanced thereby eliminating or reducing the transverse pressure forces acting on the rotor bearings. In any case, the portion of the pumping chamber cavity between two adjacent flat springs progressively decreases in size as the springs traverse the pumping arc. Conversely, that cavity progressively increases as the springs traverse the intake arc.

Numeral I4 designates a circular rotor that is formed with a central opening 16 through which a drive shaft may be positioned. Flats 18 in the opening 16 permit torque transfer to occur between the drive shaft and the rotor l4.

Seven U-shaped recesses 20 are formed on the periphery of the rotor 14 at even, angularly spaced locations. These communicate with an arcuate outlet port 22, and with an arcuate inlet port 24 formed in the body 10. Port 24 communicates with inlet opening 26 through which pumping fluid is supplied to the pump mechanism. Outlet port 22 is in fluid communication with outlet opening 28 which is connected hydraulically to pressure sensitive parts of a hydrostatic system.

Located between each of the recesses 20 is a flat surface 30, which may form a cord of the circular periphery of the rotor 14. Each flat surface 30 extends to a shoulder 32, which may be slightly undercut as indicated.

A flat spring 34 is situated adjacent each flat surface .30 and is preloaded so that its center region 36 slidably engages the circular wall of the bore 12 as the rotor rotates in a counterclockwise direction as viewed in FIG. l. The trailing edge of each flat spring 34 engages a shoulder 3.2. Directional arrow 38 indicates the direction of rotation of the rotor.

In FIG. 1, numeral 40 designates a tangent point between the bore 12 and the rotor 14. The eccentricity e indicated in FIG. 1 creates a crescent-shaped cavity in the bore 12 thereby producing a pumping chamber.

The maximum spacing between the rotor and the wall of the pumping chamber occurs at point 42.

As the springs 34 move from position 40 to the end of the intake port 24, fluid is drawn into the expanding cavities between each adjacent pair of springs 34. The term intake arc" describes the path of arcuate movement of each recess 22 when it receives intake fluid from port 24. These individual pumping cavities communicate with intake port 24 through the recesses 20 as explained previously.

One of the openings 20 passes the end 44 of the intake port 24 substantially at the same instant that the adjacent, forwardly disposed opening 20 uncovers the edge 46 of the outlet port 22. As soon as this occurs, the forwardly disposed outer surface of the adjacent flat spring 34 is subjected to the pressure in the outlet port 22 because the cavity between that flat spring 34 and the rotor 14 decreases in size. The instant point 42 is passed, a pressure exists on the other side of the spring. The fluid on the underside of each spring then is pumped forwardly and through the preceding opening 20 into the outlet port 22. Simultaneously, fluid is displaced from the cavity defined in part by the outermost surface of the flat spring 36. The portion of the total arcuate travel of any recess 22 during which it is subjected to increasing pressure is called the pumping arc." A pumping action thus occurs due to the displacement of fluid from the cavity immediately preceding each individual flat spring as well as due to the pumping action caused by the expansion and contraction of the cavity directly under each flat spring. The combined output of each pumping action, however, is received by the same outlet port 22.

As each flat spring 34 traverses the pumping arc, the leading edge 43 slides on the flat surface 30 as the trailing edge is held fast against the associated shoulder 32.

As soon as the trailing edge of the inlet port 24 is crossed by one of the openings 20, the low-intake pressure acting on the outer surface of the next forwardly disposed flat spring 34 ceases and it is replaced by high-pressure as the spring 34 enters the pumping spool. The sum of the forces acting in a radially outward direction on the individual springs exceeds the sum of the forces acting in a radially inward direction as the individual springs begin to enter the pumping arc. Thus each spring is capable of maintaining an effective seal between the inlet side of the pump and the outlet side of the pump.

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A recess 50 is formed in the rotor below each spring. This provides fluid communication between the inlet port and the underside of the spring after the preceding recess powers the inlet port cutoff edge. The recess 50 then will permit displacement of fluid from the region between the spring as the spring is compressed upon rotation through the pumping arc.

Having thus described a preferred form of my invention, what I claim and desire to secure by US. Letters Patent is:

1. A positive displacement pump comprising a pump body,

a pumping chamber formed in said body, a rotor situated in said pumping chamber, a plurality of shoulders formed on the periphery of said rotor, flat springs engaging said shoulders, each spring having a central region engageable with the surrounding wall of said pumping chamber and having a trailing edge engageable with a separate one of said shoulders, the forward edge of each spring being adapted to slide on said rotor as each spring is deflected during rotation of said rotor, an inlet port and an outlet port in said pump body communicating with said pumping chamber, each portion of said pumping chamber intermediate adjacent pairs of spring elements being in fluid communication with said outlet port as said springs traverse the arcuate extent of said outlet port, each portion of said chamber between two adjacent pairs of springs being in fluid communication with said inlet port when said springs traverse the arcuate extent of said inlet port.

2. The combination as set forth in claim 1 wherein said rotor is provided with a plurality of evenly spaced, radially disposed openings, said openings being in communication with the space between each adjacent pair of springs and communicating alternately with said inlet port and said outlet port.

3. The combination set forth in claim 1 wherein the portion of said chamber on the inward side of each spring between the spring and said rotor is in fluid communication with said outlet port as said spring traverses the arcuate extent of said outlet port and being in fluid communication with the inlet port as said springs traverses the arcuate extent of said inlet port.

4. The combination set forth in claim 2 wherein the portion of said chamber on the inward side of each spring between the spring and said rotor is in fluid communication with said outlet port as said spring traverses the arcuate extent of said outlet port and being in fluid communication with the inlet port as said springs traverses the arcuate extent of said inlet port. 

1. A positive displacement pump comprising a pump body, a pumping chamber formed in said body, a rotor situated in said pumping chamber, a plurality of shoulders formed on the periphery of said rotor, flat springs engaging said shoulders, each spring having a central region engageable with the surrounding wall of said pumping chamber and having a trailing edge engageable with a separate one of said shoulders, the forward edge of each spring being adapted to slide on said rotor as each spring is deflected during rotation of said rotor, an inlet port and an outlet port in said pump body communicating with said pumping chamber, each portion of said pumping chamber intermediate adjacent pairs of spring elements being in fluid communication with said outlet port as said springs traverse the arcuate extent of said outlet port, each portion of said chamber between two adjacent pairs of springs being in fluid communication with said inlet port when said springs traverse the arcuate extent of said inlet port.
 2. The combination as set forth in claim 1 wherein said rotor is provided with a plurality of evenly spaced, radially disposed openings, said openings being in communication with the space between each adjacent pair of springs and communicating alternately with said inlet port and said outlet port.
 3. The combination set forth in claim 1 wherein the portion of said chamber on the inward side of each spring between the spring and said rotor is in fluid communication with said outlet port as said spring traverses the arcuate extent of said outlet port and being in fluid communication with the inlet port as said springs traverses the arcuate extent of said inlet port.
 4. The combination set forth in claim 2 wherein the portion of said chamber on the inward side of each spring between the spring and said rotor is in fluid communication with said outlet port as said spring traverses the arcuate extent of said outlet port and being in fluid communication with the inlet port as said springs traverses the arcuate extent of said inlet port. 